Field of the Invention
The present invention relates to a transmission for a vehicle. More particularly, the present invention relates to a transmission for a vehicle that can improve fuel consumption and power performance by minimizing a power loss at a low speed and a high speed and by enlarging a width of a shift ratio using a plurality of external gear sets and a continuously variable transmission mechanism (CV).
Description of the Related Art
When transferring rotation power that is output from an engine through a fluid type of electric motion means such as a torque converter or fluid coupling, a common continuously variable transmission (CVT) continuously shifts rotation power thereof by a CV and transfers the shifted rotation power to an output shaft.
The CV includes variable pulleys that are disposed at each of a driving side and a driven side and a metal belt that connects variable pulleys of the driving side and the driven side, and is a device that continuously controls a shift ratio by controlling widths of the opposing variable pulleys by a hydraulic pressure.
The shift ratio is obtained by detecting driving conditions such as a vehicle speed, an engine rotation speed, and a load and by controlling opening of a shift ratio control valve that is connected to variable pulleys of the driving side and the driven side according to a preset shift pattern.
A two-stage range shift continuously variable transmission of which research and development have been actively performed is generally formed with a front and reverse driving and shift gear control means including at least one planetary gear set, a shift ratio variable means including a CV, and at least one external gear set to perform continuous shifting of two forward speeds and one reverse speed.
However, as described above, in a two-stage range shift continuously variable transmission, as at least one planetary gear set is applied, the two-stage range shift continuously variable transmission has a large volume while having a complex configuration and is thus disadvantageous in view of mounting and weight, and this is detrimental for enhancement of fuel consumption.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.